Return-Path: <13brv3@bellsouth.net> Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 165960 for flyrotary@lancaironline.net; Thu, 17 Jun 2004 09:05:21 -0400 Received: from rad ([65.6.194.9]) by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040617130449.FYSC5506.imf21aec.mail.bellsouth.net@rad> for ; Thu, 17 Jun 2004 09:04:49 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Fuel Delivery - Vapor Lock Date: Thu, 17 Jun 2004 08:04:53 -0500 Message-ID: <011001c4546b$ae86f310$6001a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0111_01C45441.C5B0EB10" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0111_01C45441.C5B0EB10 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable A couple of questions... Your pumps, filters, and regulator is in the cockpit, not in the tank as in 99.9% of the automobiles today?=20 =20 Correct. No good way to put the pumps in an RV wing tank. =20 How far are your pumps from the tank fitting, and what size line = feeds the pumps.=20 =20 The distance from the pickup, to the fuel pump inlet is less than 2 = feet, and would be gravity fed until about the last 5 gallons or so of the = tank. =20 Do you run mogas?=20 =20 Yes. 87 octane. =20 If you do run mogas, do you know the vapor pressure of the fuel = you're running? Do you test it?=20 =20 Nope, and nope. =20 I have read that mogas has a lower vapor pressure, which means it can vapor lock easier than 100LL. =20 =20 That's what I've always heard as well. I've also heard that they modify = the vapor pressure for temp, so the worst case would be a hot day, in the winter. I've always wondered if they even bother changing the mixture = here in FL though. =20 Have you tested your installation to see if it will re-prime if you inadvertently run a tank dry?=20 =20 I haven't done that particular test, but the first time I ran the pumps after filling the tanks, the fuel pressure was almost instantaneous. = I'll make a mental note to try this again when I get the tank low enough to easily drain the remaining fuel. Since I stole Tracy's fuel system, I = only feed from one tank. If I run that dry, I would first have to transfer = fuel (fairly slowly) from the other tank, then worry about priming the pumps. = In other words, I don't plan to run the tank dry when there's any fuel in = the other tank. I realize this is easier said than done, but that's the = plan. =20 Cheers, Rusty (hoping I don't get hit by lightning when I have a fuel leak) ------=_NextPart_000_0111_01C45441.C5B0EB10 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
 A couple of questions... Your pumps, filters, and regulator = is in the=20 cockpit, not in the tank as in 99.9% of the automobiles today? 
 
Correct.  No good way to put the pumps in an RV = wing=20 tank.
 
   How far are = your pumps=20 from the tank fitting, and what size line feeds the pumps. 
 
The distance=20 from the pickup, to the fuel pump inlet is less than 2 feet, and would = be=20 gravity fed until about the last 5 gallons or so of the=20 tank.
 
   Do you run = mogas? 
 
Yes.  87=20 octane.
 
   If you do run = mogas, do=20 you know the vapor pressure of the fuel you're running?  Do you = test=20 it? 
 
Nope, and=20 nope.
 
   I have read = that mogas=20 has a lower vapor pressure, which means it can vapor lock easier than=20 100LL.  
 
That's what=20 I've always heard as well.  I've also heard that they modify the = vapor=20 pressure for temp, so the worst case would be a hot day, in the=20 winter.  I've always wondered if they even bother changing the = mixture here=20 in FL though.
 
Have you tested your installation to see if it will re-prime if you = inadvertently run a tank dry? 
 
I haven't=20 done that particular test, but the first time I ran the pumps after = filling the=20 tanks, the fuel pressure was almost instantaneous.  I'll make a = mental note=20 to try this again when I get the tank low enough to easily drain the = remaining=20 fuel.  Since I stole Tracy's fuel system, I only feed from one = tank.  If I run that dry, I would first have to transfer fuel = (fairly=20 slowly) from the other tank, then worry about priming the pumps.  = In other=20 words, I don't plan to run the tank dry when there's any fuel in the = other=20 tank.  I realize this is easier said than done, but that's the=20 plan.
 
Cheers,
Rusty (hoping=20 I don't get hit by lightning when I have a fuel=20 leak)
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